1. Field of the Invention
This invention relates to office printers, and more particularly concerns improvements in ribbon cartridges, especially film ribbon cartridges, and attachments therefor.
2. Description of the Prior Art
In the prior art, ribbons made of nylon have been used in office printers and have proven to be long lasting. Both sides of the ribbon may be used. Also, the nylon ribbons may be re-inked and re-used. It is comparatively new to have film ribbon stuffed in a fan-folded manner in a cartridge, like nylon ribbon has been stuffed for a number of years.
In the prior art, film ribbons have produced a better printing image than that produced by the nylon ribbons, and have been cleaner to handle since they are inked on only one side. But they have had a shorter life than nylon ribbons, with a typical film ribbon having only 20% to 30% of the life of a nylon ribbon.
A ribbon cartridge includes a plastic case and cover, a ribbon folded in the body of the case and cover, drive means for advancing the ribbon outside the case and cover, and springs to apply tension to the ribbon. The ribbon cartridge is placed in a printer and is used in common EDP (Electronic Data Processing) applications.
The printer advances the drive means located in the cartridge body, and a guide system around the printer head guides the inked ribbon to place it in position for printing.
In general, there are two different types of inked ribbons in a ribbon cartridge, nylon ribbon and film ribbon.
In the nylon ribbon, the substrate is impregnated with a special ink formulated for impact printing, and the nylon ribbon with its fibers build up an ink reservoir, and provides ink in front of the printer head in a consistent manner. The nylon ribbon is folded in an organized fashion in a stuffing box in the ribbon cartridge so that it pulls out smoothly and evenly.
It is common in nylon cartridges to twist the ribbon by 180 degrees. This twisting is called a "Moebius-loop", and the advantage of this configuration is to achieve a higher use of the ribbon by using more of it. The printing track may be on both the top edge portion of the ribbon and on the bottom edge portion of the ribbon. It can improve the print life of the nylon ribbon cartridge up to about 90% over the cartridge wherein the ribbon is not twisted by 180 degrees.
On the other hand, a film ribbon consists of a base material, which may be Mylar film, and a coating which may be a black solvent ink coating. The coating is applied to only one side of the film, and is placed so that it faces the paper when installed in front of a printer head. The film is stored in a stuffing box in the cartridge and is folded in the same way as a regular nylon ribbon, but it cannot be twisted by 180 degrees. The "Moebius" system cannot be used because the film ribbon is coated on only one side. The film cannot be coated on two sides because of the abrasiveness of the coating and because of surface conditions. Therefore, the life of a film ribbon cartridge is significantly lower than the life of a nylon ribbon cartridge using the "Moebius-loop".
It is an object of this invention to increase the life of film ribbons to make it closer to the life of nylon ribbons.